Abraham H. Foxman, a hidden child of the Holocaust who became the chief warrior against antisemitism in the United States as national director of the Anti-Defamation League for almost three decades, died Sunday in Manhattan. He was 86. His death, at a hospital, was confirmed by his son, Ariel. Foxman spent half a century working for the ADL, and from 1987 to 2015 was its chief executive. Whenever there was an incident that displayed hatred or hostility toward Jews — a synagogue firebombing, an unprovoked stabbing of a skullcap-wearing young man or a celebrity’s bigoted remark — Foxman would be called on for a public comment. His well-earned indignation, a streetwise, sometimes pugnacious, voice and a gift for articulating the fine distinctions of an issue made his comments stand out from more diplomatic responses by leaders of other Jewish groups.…